Apparatus for the densification and energization of charged particles



Dec 18 1962 R. F. POST ETAL FOR THE DENSIFICATION AND TION OF CHARGED PARTICLES Flled Aug. 9, 1961 2 Sheets-Sheet l 6138 5 E20. dd mm NM mm vm INVENTORS. RICHARD F POST M258 556m M853 wwwmwwm P553 EMEWSQ :fimEG 83E $6 5m 86 51 BY FREDERIC H. COENSGEN WWW ATTORNEY.

Dec. 18, 1962 R. F. POST ETAL 3,069,34

APPARATUS FOR THE DENSIFICATION AND ENERGIZATION 0F CHARGED PARTICLES Filed Aug. 9, 1961 2 Sheets-Sheet 2 I FIG. 2.

AXIAL POSITION, z

LLI

INVENTORS. AXIAL osmom, 2 FIG. 3. RICHARD E PosT BY FREDERIC H. COENSGEN ATTORNEY.

Bfifififid l Patented Dec. 18, 1962 3 669 344 APPARATUS ran "this DENSll lCATlN AND ENERGEZATEGN 0F CHARGED PAREHILES Richard F. Post, Walnut Creek, and Frederic H. Coensgen, leasanton, Caiifi, assignors to the United States of America as represented by the United States Atomic Energy Commission Filed Aug. 9, 1951, Ser. No. 136,686 9 Claims. (Cl. 294-1932) The present invention relates generally to the production and accumulation of high energy charged particles at high density, and more particularly to apparatus for materially increasing the energy and density of a plasma to produce various nuclear reactions between the plasma particles.

This application is a continuation-in-part of our prior application S.N. 736,646, filed May 20, 1958, now abandoned.

In the field of nuclear physics it is often times desirable to provide accumulations of high energy particles at high densities. Energetic ions or electrons may, for example, be advantageously accumulated into high density hunches and periodically directed into charged particle accelerators or other utilization equipment. Electric fields have long been employed for the foregoing purpose in various ion sources, electron guns, and the like, wherein ions or electrons are accelerated to relatively high energies during discrete periodic intervals of time by pulsed electric fields to thereby form densified bunches of high energy particles. In other instances recently of importance, particularly in the field of magnetohydrodynamics, it has become desirable to provide dense accumulations of a space-charge neutralized mixture of ions and electrons, i.e., a high density, high energy plasma. The accumulations of such plasma may be injected into various controlled fusion devices and further densified and energized therein to establish conditions requisite to the initiation and promotion of nuclear reactions. The accumulations of plasma may in other instances be initially of suflicient energy and density to establish a thermonuclear reaction without additional energization and densification or at least to establish other nuclear reactions through interparticle collisions which are productive of neutrons, X-rays, and other radiation useful for manifold utilitarian purposes. It will be appreciated that the previously-mentioned electric fields for individually accelerating and accumulating ions or electrons are unsatisfactory for accomplishing similar functions with a plasma, inasmuch as any attempt to influence a plasma by electric fields produces plasma disintegration. For example, an electric field of such polarity that it would attract positively charged ions in a plasma would repel electrons so that the field would terminate the plasma instead of accelerating same.

In order to accelerate plasma to high energy and accumulate same in densified quantities, means other than electric fields must be employed and in this connection one solution to the problem is presented in a copending application for U.S. Letters Patent of Richard F. Post, Serial No. 443,447, filed July 14, 1954. Briefly, the invention disclosed in said copending application comprehends the employment of a magnetic containment system generally characterized by an axially symmetric magnetic field having spaced gradientially-intensified reflector field regions situated therein and providing a containment zone for charged particles in an evacuated space. The application also discloses methods and means for the injection, trapping, heating (energization), compression, containment, and decompresion of charged particles (plasma) and the utilization of the products of various reactions which may be caused to occur. The term Pyrotron has been conceived to designate devices and processes of the general character disclosed in the said copending application and one particularly useful embodiment and certain processes pertaining thereto disclosed in the application relate to a linear multiple zone Pyrotron. A linear multiple zone Pyrotron generally includes a magnetically contained accumulator and initial compression zone defined by an axially symmetric magnetic field having axially spaced gradientially-intensified reflector field regions situated therein. In coaxial abutment with the accumulator zone there is also provided a magnetic containment reaction and secondary compression zone defined by an axially symmetric magnetic field extending from one of the accumulator reflector field regions to a third reflector field region axially spaced apart therefrom. The intensity of the central field region between the reflector field regions of the accumulator zone is less than that of the similar central field region of the reaction zone. Charged particles (plasma) under low density conditions are introduced to the accumulator zone and initially compressed by increasing the intensity of the corresponding central field region and terminally bounding reflector field regions. Such compression results in densification and heating (increased energization) of the particles to predetermined intermediate values. The plasma of intermediate density and energy is next accelerated into the reaction zone by appropriate axial translation of the accumulator fields to positions coinciding with the reaction zone. The reaction zone fields are then increased in intensity to further compress the plasma and thereby increase the density and energy of the plasma particles to values greater than the intermediate values attained in the accumulator zone. The plasma may be further densified and increased in energy in step-wise fashion through the employment of additional successive compression zones. In this manner plasma may be accumulated at substantial densities and energies commensurate with the establishment of controlled thermonuclear reactions, or at densities and energies useful for other purposes.

The present invention is of generally similar relevance to the multiple zone Pyrotron discussed above and provides improved specific structure for accomplishing the dcnsification and energization of charged particles (plasma) in a plurality of successive magnetically contained compression zones of progressively greater magnetic intensity. Charged particles (i.e., ions and electrons) may be introduced to the first compression zone in admixture as a plasma, and accelerated through the successive compression zones of progressively greater intensity until the particles are finally accumulated in the last compression zone at high densities and energies. The present invention is accordingly useful as a novel charged particle magnetic linear accelerator. Where plasma is accumulated at sufficient energy and sufiicient density in the device of the present invention, conditions requisite to the initiation and/or promotion of thermonuclear reactions as well as other nuclear reactions are established with an attendant production of energetic neutrons and other nucleons useful for serving manifold utilitarian purposes.

it is therefore an object of the present invention to provide apparatus for producing dense accumulations of extremely energetic charged particles.

Another object of the present invention is the provision of a magnetic linear accelerator for space charge neutralized particles.

Still another object of the invention is to provide means for increasing the energy and density of a plasma.

It is yet another object of the invention to accelerate a plasma.

An important object of the invention is to provide hi h final magnetic compression fields over small plasma ace-9,344 V volumes to efficiently utilize magnetic energy in a Pyro tron.

A One other object of this invention is to provide means for initiating and promoting controlled thermonuclear reactions as well as other nuclear reactions with an at tendant production of energetic nucleons.

It is a further object of the present invention to provide a muliple zone Pyrotroii. V I

Other objects and advantages of the invention will become apparent by consideration of the following de scription taken in conjunction with the accompanying drawings, of which:

FIGURE 1 is a cross sectional plan view, partially in schematic, of a preferred embodiment of the invention;

FEGURE 2 is a graphical schematic illustration of the axial magnetic field intensity profile of the embodiment of FIG. 1; and

FIGURE 3 is a graphical illustration of the axial magnetic field intensity profile of this embodiment at several successive increments of time.

Considering now the invention in some detail and referring to the illustrated form thereof in the drawings, there is provided generally a linear succession of communicating magnetically contained evacuated compression chambers for charged particles. Charged particle source means communicating with the first one of the compression chambers inject charged particles thereinto as a space charge neutralized mixture of particles of both polarities, i.e., as a plasma. Means are provided to generate a magnetic compression field within the first chamber and the field is manipulated to compress the particles (i.e., increase the kinetic ener y of the particles while restricting same to a limited region) by an intermediate amount. During compression the field is further manipulated to transfer the particles axially into the next successive compression chamber and to trap the particles therein. Means are provided to generate a mag-, netic compression field within the second chamber and the field is manipulated to further compress the particles and transfer same into the next axially successive charm her. In a like manner the particles are further compressed in each successive chamber whereby there is accumulated in the last chamber a densified charge of. high energy particles.

Preferred structure for providing an evacuated region in which to establish the compression chambers mentioned above, as illustrated in FIG. 1, comprises an elongated closed vacuum envelope 11 having a plurality of graded cylindrical sections 12, 13, 14 of progressively decreasing diameters and lengths. The'respective volumes 16, 17, 13 enclosed by sections 12, 13, 14 are accordingly progressively decreasing and each enclosed volume corresponds to one of the compression chambers of previous mention. Envelope 11 in addition includes a port 19 or equivalent means to facilitate communicable connection of a vacuum pump (not shown) to the interior of the envelope for the purpose of evacuating same to suitable high vacuum dimensions, e.g., of the order of lO mm. of mercury.

Appropriate magnetic field generating means are carried by envelope 11 to generate the hereinbefore-mentioned axially symmetric magnetic compression fields within compression chambers 16, 17, 18. Such field generating means preferably includes a pulse solenoid 21 disposed coaxially about envelope tubular section 12 and extending over at least a portion of the axial length thereof with one end proximate the stepped transition from section 12 to section 13. Solenoid 2'1, moreover, is best formed in several axially spaced sections of varying turnsdensity and length in order to provide a shaped, nodal pulsed field which gradually decreases in intensity along the axis of section 12 toward section 13. It will be appreciated that a single solenoidal section having a suitably tapered turns-density distribution or equivalent The magnetic compression field generating means of the present invention further includes a pair of pulse solenoids 23, 24 disposed in spaced-apart relation coaxially about envelope section 14- proximate the transition from. section 13. Solenoids 23, 24 are preferably serially connected and upon energization generate a pair of spaced reflector fields forming a Pyrotron magnetic containment. field of the general character disclosed in the previously-' mentioned copending application of Richard F. Post Se rial No. 443,447.

In addition to the pulse solenoids described above, the magnetic compression field generating means include a. plurality of direct current solenoids 26 disposed in axially spaced apart relation co-axially about pulse solenoid 2 and the remaining length of envelope section 12; Similarly, a plurality of axially spaced direct current solenoids- 27 are mounted coaxially about pulse solenoid 22, and axially spaced direct current solenoids 28 are mounted coaxially about pulse solenoids 23, 24. Finally, an end reflector field direct current solenoid 29 is mounted concentrically about the end region of envelope section 14 in abutment with the end of pulse solenoid 24. Solenoids 26 preferably have a lesser turns-density than solenoids 27' which, in turn, have a lesser turns-density than solenoids 28. Reflector field solenoid 29, moreover, preferably has a greater turns-density than solenoids 28. With the foregoing relations between the turns-density of the direct current solenoids, such solenoids may be connected in electrical series and coupled between the terminals of a DC. power source 31 to facilitate energization thereof. By virtue of the turns-density variation between the respective direct current solenoids 26, 27, 28- and reflector field solenoid 29, a direct current axially symmetric magnetic field is generated within envelope 11 having an intensity which increases progressively in steps in each successive compression chamber 16, 17, 18 and which rises sharply to a reflector field peak in the end region of the last chamber 13. More particularly, the direct current magnetic field in accordance with the present invention has an axial intensity profile as is generally depicted by the solid line curve in FIG. 2. As illustrated therein, the direct current magnetic field has a uniform relatively low intensity H in compression cham ber 16 and then increases smoothly to a second relatively greater uniform intensity H in compression chamber 17. The field intensity then increases abruptly from intensity H to an even greater intensity H which extends uniformly through compression chamber 18 to the end thereof and then rises sharply to a reflector field peak intensity, H,-. In order that a tube of flux of the direct current field threads the entire length of envelope 11 without intersecting a wall thereof, the turns-density of the direct current solenoids are chosen such that the corresponding magnetic field intensities H H H thereby generated within adjacent compression chambers vary inversely as at least the ratio of the diameters of the corresponding envelope sections 12, 13, 14. Accordingly, the magnetic field intensities H H within chambers 17, 18 relative to the intensity H Within chamber 16 are given by the following expressions:

12 o H1Z(D2 The ends aoeaeaa where It is to be noted that means other than the series energized direct current solenoids of varying turns-density described above may be employed to generate a direct current magnetic field of the configuration depicted by FIG. 2 and therefore same are not to be construced as limiting upon the scope of the invention. For example, the turns-densities of solenoids 26, 27, 28, 29 may be equal and such solenoids connected to direct current sources of progressively greater magnitude to generate the indicated field.

Considering now means for energizing the pulse solenoids 21, 22, 23, 24 of previous mention in order to provide pulsed components of the magnetic compression field of the present invention, pulsed current sources 32, 33 are respectively connected to solenoids 21, 22 and pulsed current source 34 is connected to solenoids 23, 24 in additive series. Such current sources 32, 33, 34 are capable of generating very fast rise time pulses of current of predetermined maximum values when connected to the corresponding pulse solenoids. The current sources may accordingly advantageously be capacitor banks peri odically charged to high voltage by a direct current voltage supply with the capacitance of the banks being selected relative to the inductance of the pulse solenoids to produce periods of sinusoidal current oscillation in the resultant oscillatory circuits commensurate with the desired rise times. The pulsed current sources may in addition include variable resistors in the output circuits thereof to facilitate adjustment or" the magnitude of current flow through the solenoids to substantially any desired value. More particularly, the pulse current sources 32, 33, 34 are preferably arranged to produce current pulse rise times in the corresponding solenoids 21, 2.2, and 23, 24 of progressively longer durations. The peak current mag nitude in pulse solenoid 22 moreover is adjusted such that the corresponding peak intensity H (see the dashed line curves of FIG. 2) of pulsed magnetic field component thereby generated in compression chamber 16 when combined with the direct current field component of intensity H exceeds the direct current field intensity of H established in compression chamber 18. Similarly, the peak magnitude of pulse current supplied from source 33 to solenoid 22 is adjusted such that the resulting peak intensity 1-1 of pulsed magnetic field component established in compression chamber 17 in combination with the direct current field component intensity H established therein, exceeds the intensity of reflector field peak H,. The pulse current peak magnitude supplied from source 34 to solenoids 23, 24 is also of a value such that the peak intensities H H of the spaced reflector field regions thereby established in compression chamber 18 when combined with the direct current field component intensity H exceed the intensity of direct current reflector field H by substantially any desired amount.

To facilitate establishment of the foregoing pulse field components H H H and H in respective succession, pulse current sources 32, 33, 34 are connected to pulse solenoids .21, 22, and through suitable sequential switching means 36. Such switching means are designed to initially effect connection of source 32 to solenoid 2 whereupon such solenoid is energized with fast time rising current and the time rising pulse component of magnetic field is generated in compression chamber 16. By virtue of the turns-density distribution in the various sections of solenoid and the stepped configuration of the direct current field component within envelope the overall compression field configuration within envelope 11 for several successive increments of time is as generally depicted by the axial intensity profile of FIG. 3. More particularly, at a time, t just after time rising current begins to flow through solenoid 21, the compression field in compression chamber 16 includes a central region of relatively low intensity H terminally bounded on one side by a region of relatively high intensity H and on the other side by the direct current stepped region of relatively high intensity H existing in compression chamber 17. At a later time t the pulse current magnitude is increased to a value commensurate with a central field region of intensity H greater than the intensity i1, and terminally bounded on one side by the stepped region of higher intensity H and on the other side by a region of relatively high intensity H greater than H At a still later time, during the rise time of the pulse current, the magnetic field within compression chamber 16 increases axially from the value H in chamber 17 to a value of greater intensity H in the terminal region of chamber 16. The magnetic field within chambers 16, 17 at time t is accordingly defined by a region of the intensity H within chamber 17 terminally bounded on one side by the region of greater intensity H within chamber 16 and on the other side by the region of relatively greater intensity H existing within chamber 18. The field intensity within chamber 16 continues to in crease until at a time t the current pulse applied to solenoid 21 attains peak amplitude. The nodal magnetic field established within compression chamber 16 at time i is accordingly of the peak intensity, H of previous mention which is greater than the direct current field intensity H existing within compression chamber 18.

Substantially simultaneously with the attainment of maximum current in solenoid 2'1 (i.e., at time t sequential switching means 36 effects connection of pulse current source 33 to solenoid 2-2. Time rising pulsed current thus commences to fiow through solenoid 2'2 and the configuration of the overall magnetic compression field established Within compression chamber 17 is initially generally similar to that previously existing at time t within chamber 16 as described above. More particularly, the compression field within chamber 17 includes a central region of relatively low intensity terminally bounded on one side by the stepped region of relatively high intensity H established in compression chamber 18 and on the other side by a time rising nodal region of relatively high intensity. The intensities of the central region and nodal region continue to increase with respect to time until the current pulse applied to solenoid attains maximum amplitude at which time the central field region exceeds the intensity H Within compression chamber 18. The magnetic field configuration at this time is accordingly as depicted by the profile curve H;.H H of FIG. 2.

Upon the attainment of peak current in solenoid 2.2, sequential switching means 36 effects connection of pulse current source 3 to solenoids 23, 2-1- resulting in the generation of axially spaced gradientially-intensified retlector field regions bounding a less intense central region within compression chamber 18. The intensity of the foregoing field rises in time until peak current flows through solenoids 23, 2 and the peak magnetic intensity profile curve H I-l of FIG. 2 is attained.

As regards circuitry which may be employed as sequential switching means 36, a variety of satisfactory circuits will suggest themselves to those skilled in the art. For example, circuits in general accordance with teachings of a copending application for U.S. Letters Patent of Richard F. Post et al., Serial No. 715,157, filed February 13, 1958, now Patent No. 3,015,148, issued January 2, 1962, may be advantageously employed as the sequential switching means 36 of the present invention.

It is to be noted that the magnetic compression fields established Within compression chambers lo, l7, 18- in aces,

the manner described above are effective in the progressive densificati I introduced to the first chamber at: in a manner which follows from the considerations disclosed in the former copending application of Richard F. Post, Serial No. 443,447, and which are described hereinafter. Accordingly, to introduce charged particles as a space charge neutralized mixture to compression chamber 18, a suitable source 37, or array thereof, is mounted within the chamber interiorly of envelope section 12;. Source 37 may include conventional ion sources and electron guns to inject ions and electrons in neutralized qu. ties. Alternatively, a plasma generator may be employed as source 37. For a detailed description of a suitable plasma generator, reference may be had to a copending application for US. Letters Patent of Winston H. Bostick et al., Serial No. 589,831, filed June 6, 1956, now Patent No. 2,900,548. Source 37, moreover, is preferably pulsed and is di posed axially outward from pulse solenoid 21. The source is thus located in the direct current component of magnetic compression field of intensity L and outside of the pulsed component of field generated by solenoid 21. Source 3-7 is preferably triggered at a time prior to the generation of the pulsed field and to accomplish this end the source is responsively a connected to a trigger generator 31. The output of the trigger generator is also coupled through suitable time delay means 39 to sequential switching means 36 for the purpose of commencing operation of the latter in delayed time relation to the triggering of source 37.

With the apparatus of the present invention constructed and energized as described above, a cycle of operation is commenced by the generation of a pulse at the output of trigger generator 38. Such pulse triggers particle source 37 resulting in the generation of plasma particles in the first compression chamber 16 established within envelope section 12. The particles difiuse along helical paths centered about the magnetic lines of force established within the chamber due to the direct current corn ponent of magnetic compression field of intensity H After the short time delay due to time delay means 39, during which the charged particles fill the volume surrounded by pulse solenoid 21, the pulse generated at the output of trigger generator 38 initiates operation of sequential switching means 36. As a result, the pulse solenoid 21 is energized and the time rising pulsed component of compression field is established in chamber 16 inwardly from source 37. During the initial portions of rise time of the pulsed field component the overall compression field in chamber 16 has a configuration as generally depicted by the curve H H -H of FIG. 3 and such field configuration is efiective in trapping the charged particles filling the volume under solenoid 21. As the field rises in time, the charged particles are compressed and the diameter of the charged particle column trapped between the gradientially-intensified end regions of the field (e.g., H and H decreases. The charged particle density accordingly increases and the particle kinetic energy associated with the velocity component perpendicular to the direction of the magnetic field increases. The manner in which the foregoing densification, energization, etc. is accomplished in the compression field is disclosed in the previously referenced application of Richard F. Post, Serial No. 443,447, and accordingly is not described in detail herein. It is to be noted, however, that in the present invention, the compression field in compression chamber 16 is relatively low and therefore the initial diameter of the charged particle column is relatively large. It can be shown that the final particle energy advantageously is directly proportional to the initial diameter and therefore the particle energies attainable in the present invention are relatively large. Another advantage resulting from the relatively low initial magnetic field employed is in the increased value of the ratio of particle energy density to magnetic field energy density,

are

which ratio is proportional to a squared function of the initial diameter.

As the pulse component of compression field within chamber 16 rises further with time, and the central field region of the overall field exceeds the direct current field intensity H in chamber 1'7 (note the profile curve H -H --H, of PEG. 3), the densified and energized particles are transferred longitudinally into chamber 17. Moreover, the fast time rising field in chamber 16 preferentially accelerates the particles of greatest energy into chamber 17. At time t corresponding to peak intensity of the pulse field component in compression chamber 16 the accelerated particles of selected high energy occupy chamber 17, and at the same time sequential switching means as effects cnergization of pulse solenoid 22. As the pulse component of field rises in time, the overall compression field configuration within chamber 17 is generally similar to that previously established in chamber 16' as described above, but of a higher initial intensity. The charged particles are further densified and energized in chamber 17 in the manner hereinbefore described in relation to chamber 16, and the particles are similarly transferred selectively as to energy longitudinally into chamber 18.

Simultaneously with the attainment of maximum field in chamber 17, pulse solenoids 23, 24 are simultaneously energized by action of sequential switching means 36. The time rising magnetic containment field depicted by the profile curve H H of FIG. 2 is thereby generated resulting in trapping and further densification and energization of the particles in chamber 18. There is thus provided in the last chamber 18, an extremely dense, energetic accumulation of charged particles in a plasma. The plasma particles may be extracted axially from chamber 18 for use in utilization apparatus as by simultaneously decreasing the intensities of pulse reflector field H and direct current reflector field 1-1,. The foregoing may be accomplished by simultaneously short circuiting solenoids 24, 29 with appropriate electronic switches or equivalent means (not shown). Where a sufficient number of compression chambers are employed with fields of suitably high magnitudes and plasma of sufi'iciently high initial energy in the apparatus of the present invention, the resulting density and energy of the plasma particles in the last chamber are commensurate with the initiation and promotion of controlled thermonuclear reactions. Various nuclear processes may thereafter be conducted in chamber 13 in accordance with conventional Pyrotron practice as disclosed in the copending Post application, Serial No. 443,447.

One of many possible sets of parameters that might be employed with the basic apparatus described hereinbefore is as follows.

Vacuum chamber:

Plasma source:

Type stacked deuterated titanium ring Quantity-9 sources in distributed annular array Output- 5 X it) ions per source (approximately half 13+ ions and remainder predominantly multiply charged titanium ions) Deuteron current10 amperes Output energy-83i) e.v.

Magnetic bias field: Kilogauss H 0.5 H 2 H 12 H 24 Pulsed magnetic field:

Hf-combined peak magnitude as superimposed on bias field-12 kilogauss Rise time10 nsec. Initiation time10 ,usec.after sources fired. H 'combined peak magnitude as superimposed on bias field-24 kilogauss Rise time-50 ,uSCC. Initiation time30 ,usec.after sources fired. r2 r1" Combined peak magnitude of as superimposed on bias field Reflector fields-150 kilogauss Central field-75 kilogauss Rise time300 sec. Initiation time-S sec.after sources fired Decay timemsec. Ion density- Initial1() per cc. Final X per cc. Ion rotational energy Initial-400 e.V. Final10 kv.

Apparatus substantially in accordance with the above parameters has produced neutrons. The energy distribution and yield of the neutrons, analysis of the reaction products escaping from the device, and other experimental observations, moreover, all indicate that the neutrons are of thermonuclear origin.

While the salient features of the present invention have been described in detail with respect to but one preferred embodiment, it will be apparent that numerous modifications may be made within the spirit and scope of the in vention, and it is therefore not desired to limit the invention to theexact details shown except insofar as they may be defined in the following claims.

What is claimed is:

1. Apparatus for the densification and energization of charged particles comprising a linear succession of axially communicating evacuated compression chambers, means carried by said chambers for generating an axially symmetric unidirectional magnetic field therein, said field having an intensity 'which increases progressively in steps in each successive compression chamber, pulsed magnetic field generating means carried by said chambers for generating axially symmetric pulsed magnetic fields within said chambers in superimposition with said unidirectional field and in respective time sequence in the direction of increasing intensity thereof, the peak intensity of each of said pulsed fields in combination with the unidirectional field intensity in each chamber being greater than the intensity of the unidirectional field in the next successive chamber, and particle source means communicating with the first one of said chambers for introducing charged particles thereto.

2. Means for producing a dense accumulation of energetic plasma comprising an elongated evacuated vacuum envelope having a plurality of graded cylindrical sections of progressively decreasing diameter and length, magnetic field generating means carried by said envelope for generating an axially symmetric unidirectional magnetic field within said envelope, said field having an intensity increasing progressively in steps in said graded sections from a minimum in the section of largest diameter to a maximum in the section of smallest diameter, pulsed magnetic field generating means carried by said envelope for generating fast time rising pulsed magnetic fields in said sections in respective sequence from the largest to smallest diameter sections, the intensity of each pulsed field decreasing along the envelope axis in the direction of envelope sections of decreasing diameter, the peak intensity of each of said pulsed fields in combination with the unidirectional field intensity in each corresponding section being greater than the unidirectional field intensity in the next successive section, and plasma generatingmeans communicating with the section of largest diameter to inject plasma thereto whereby the plasma is compressed and translated axially from each section in succession.

3. Means as defined by claim 2, further defined by the ratio of the intensities of said unidirectional magnetic field in successive envelope sections varying inversely as at least square of the ratio of the diameters thereof.

4. Means as defined by claim 2, further defined by the rise times of the pulsed fields in successive ones of said envelope sections of decreasing diameter being of progressively longer durations.

5. Apparatus for heating plasma to high kinetic temperatures and producing nuclear radiation by nuclear reactions occurring between the energetic constituents of the plasma comprising an elongated evacuated vacuum envelope having a plurality of graded cylindrical sections of progressively decreasing diameter and length, magnetic field generating means carried by said envelope for generating an axially symmetric unidirectional magnetic field within said envelope with the field intensity in successive sections of decreasing diameter increasing progressive'ly in steps from a minimum in a first section of largest diameter to a maximum in a last section of smallest diameter and rising sharply to a reflector field peak in the terminal region of said last section, pulsed magnetic field generating. means carried by said envelope for generating fast time rising pulsed magnetic fields in said sections in respective sequence from the first section to the section preceding said last section, the intensity distribution along the envelope axis of each pulsed field decreasing in the direction of said last section, the peak intensity of each pulsed field in combination with the unidirectional field intensity in each corresponding section being greater than the unidirectional field intensity in the next successive section, pulsed magnetic reflector field generating means carried by said last section for simultaneously generating a pair of axially spaced gradientially-intensifled fast time rising reflector fields therein sequentially following the attainment of peak pulsed field intensity in the preceding section, and plasma generating means communicating with said first envelope section for injecting plasma thereto whereby the plasma is compressed in and translated axially from each section in succession to be trapped between said reflector fields in the last section and further compressed to produce nuclear radiation from nuclear reactions induced between the resulting energetic constituents of the plasma.

6. Apparatus as defined by claim 5, further defined by said pulsed magnetic field generatin means comprising a plurality of solenoids respectively concentrically disposed about said envelope sections, the turns-density of each solenoid diminishing axially toward sections of decreasing diameter, a corresponding plurality of pulsed current sources, and sequential switching means coupled between said sources and corresponding solenoids for connecting successive sources to the corresponding solenoids in time sequence.

7. A plasma linear accelerator comprising an elongated evacuated vacuum envelope having a plurality of graded cylindrical sections of progressively decreasing diameter and length, direct current solenoid means disposed concentrically about each one of said sections for generating upon energization an axially symmetric unidirectional magnetic field within said envelope with the field intensity in successive sections of decreasing diameter increasing progressively in steps, direct current source means connected to said solenoid means for effecting said energization, a plurality of pulse solenoids respectively concentrically disposed about said envelope sections, the turns- 7 ll density of eachv solenoid diminishing axially toward sections of decreasing diameter, a plurality of pulsed current sources, sequential switchingmeans coupled between said sources and said pulse solenoids for sequentially connecting the sources to corresponding successive pulse solenoids disposed about sections of progressively smaller diameter upon the attainment of peak current in respective preceding adjacent pulse solenoids, a pulsed plasma generator communicating with the envelope section of largest diameter for introducing plasma thereto, a trigger generator connected to said plasma generator to trigger same, and time delay means connected between said trigger generator and said sequential switching means for actuating the switching means in delayed time relation to the triggering of said plasma generator.

8. A plasma injector comprising an elongated vacuum envelope having a plurality of graded cylindrical sections of progressively decreasing diameter and length, a plurality of direct current solenoids disposed coaxially about said envelope sect-ions with the turns-density of said solenoids progressively increasing as the diameters of said sections decrease, a source of direct current serially connected to said direct current solenoids, a plurality of pulse solenoids respectively concentrically disposed about said envelope sections, the turns-density of each pulse solenoid diminishing axially toward the envelope sections of decreasing diameter, a plurality of pulsed current sources, sequential switching means coupled between said sources and said pulse solenoids to connectvthe sources to the solenoids in sequence in a direction from largest to smallest diameter sections and upon the attainment of peak current in each respective immediately preceding pulse solenoid, a pulsed plasma source disposed within said envelope section of largest diameter, a trigger gener ator connected to said plasma source to periodically pulse same and thereby introduce plasma to the envelope section of largest diameter, and time delay means connected between said trigger generator and said sequential switching means for actuating the switching means in delayed time relation to the pulsing of said plasma source. 7

9. Apparatus for heating plasma to high kinetic temperatures and producing nuclear radiation by nuclear reactions occurring between the energetic constituents of a plasma comprising an elongated evacuated vacuum envelope having a plurality of graded cylindrical sections progressively decreasing in diameter and length from a first section of largest diameter to a last section of smallest diameter, a plurality of direct current solenoids disposed in coaxial spaced-apart relation about each secupon energization a unidirectional axially symmetric magnetic field having anintensity which varies between successive. sections of decreasing diameter according to the relation:

a o H12 0,

where:

a direct current reflector field solenoid disposed concentrically about the end region of said last section to generate upon energization a reflector field rising sharply from the unidirectional field intensity therein to a reflector field peak, a directcurrent source connected to said direct current solenoids and reflector field solenoid in additive series to efiect said energization, a plurality of pulse solenoids respectively concentrically disposed about said envelope sections from the first section to the section preceding said last section, the turns-density of each pulse solenoid diminishing axially towardlthe last section, a plurality of pulsed current sources for connection to said pulse solenoids, said current sources upon connection to said pulse solenoids disposed about successive sections of decreasing diameter producing current pulses having successively increasing rise times, a pair of axially spaced pulsed reflector field solenoids disposed coaxially about said last section, a pulsed reflector field current source for connection; to said pulsed reflector field solenoids in series, sequential switching means coupled between said pulsed current and pulsed reflector field current sources and said pulse and pulsed reflector field solenoids to connect the sources to the solenoids in sequence in a direction from the first toward the last sections and upon the attainment of pe ak current in respective immediately preceding solenoids, a pulsed plasma source disposed within said first envelope section, a trigger generator connected to said plasma source to periodically pulse same and thereby introduce plasma to the first envelope section, and time delay means connected between said trigger generator and said sequential switching means for actuating the switching means in delayed time relation to the pulsing of said plasma source.

References Cited in the file of this patent Project Sherwood, by Amasa S. Bishop, September 1958, Addison Wesley Publishing Co., Reading, Mass, pp. 61, 63, 64-, 122-426. 

1. APPARATUS FOR THE DENSIFICATION AND ENERGIZATION OF CHARGED PARTICLES COMPRISING A LINEAR SUCCESSION OF AXIALLY COMMUNICATING EVACUATED COMPRESSIONCHAMBERS, MEANS CARRIED BY SAID CHAMBERS FOR GENERATING AN AXIALLY SYMMETRIC UNIDIRECTIONAL MAGNETIC FIELD THEREIN, SAID FIEKD HAVING AN INTENSITY WHICH INCREASES PROGRESSIVELY IN STEPS IN EACH SUCCESSIVE COMPRESSION CHAMBER, PULSED MAGNETIC FIELD GENERATING MEANS CARRIED BY SAID CHAMBERS FOR GENERATING AXIALLY SYMMETRIC PULSED MAGNETIC FIELDS WITHIN SAID CHAMBERS IN SUPERIMPOSITION WITH SAID UNIDIRECTIONAL FIELD AND IN RESPECTIVE TIME SEQUENCE IN THE DIRECTION OF INCREASING INTESITY THEREOF, THE PEAK INTENSITY OF EACH OF SAID PULSED FIELDS IN COMBINATION WITH THE UNIDIRECTIONAL FIELD INTENSITY IN EACH CHAMBER BEING GREATER THAN THE INTENSITY OF THE UNIDIRECTIONAL FIELD IN THE NEXT SUCCESSIVE CHAMBER, AND PARTICLE SOURCE MEANS COMMUNICATING WITH THE FIRST ONE OF SAID CHAMBERS FOR INTRODUCING CHARGES PARTICLES THERETO. 